Optimizing the immobilization conditions of β-galactosidase on UV-cured epoxy-based polymeric film using response surface methodology

Covalent immobilization of β-galactosidase using a novel carrier alginate/tea waste: statistical optimization of beads modification and reusability

β-galactosidase has been immobilized onto novel alginate/tea waste gel beads (Alg/TW) via covalent binding. Alg/TW beads were subjected to chemical modification through amination with polyethyleneimine (PEI) followed by activation with glutaraldehyde (GA). Chemical modification parameters including PEI concentration, PEI pH, and GA concentration were statistically optimized using Response Surface methodology (RSM) based on Box-Behnken Design (BBD). Analysis of variance (ANOVA) results confirmed the great significance of the model that had F value of 37.26 and P value < 0.05. Furthermore, the R2 value (0.9882), Adjusted R2 value (0.9617), and predicted R2 value (0.8130) referred to the high correlation between predicted and experimental values, demonstrating the fitness of the model. In addition, the coefficient of variation (CV) value was 2.90 that pointed to the accuracy of the experiments. The highest immobilization yield (IY) of β-galactosidase (75.1%) was given under optimized conditions of PEI concentration (4%), PEI pH (9.5), and GA concentration (2.5%). Alg/TW beads were characterized by FT-IR, TGA, and SEM techniques at each step of immobilization process. Moreover, the immobilized β-galactosidase revealed a very good reusability as it could be reused for 15 and 20 consecutive cycles keeping 99.7 and 72.1% of its initial activity, respectively. In conclusion, the environmental waste (tea waste) can be used in modern technological industries such as the food and pharmaceutical industry.

Fluorimetric Reusable Polymeric Sensor for Hydrogen Sulfide Detection

In this study, with the help of reactive monomers, crosslinkers, and photoinitiator that detect H2S in various matrices, an H2S sensitive fluorescence sensor polymerizes under ultraviolet (UV) light was developed. To this goal, a polymeric membrane was prepared, and the characterization of the membrane was carried out with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. Afterward, appropriate conditions were identified, the excitation wavelength was determined as 370 nm, and the emission wavelength was determined as 425 nm. It was established that the fluorescence intensity of the prepared polymeric membrane decreased in the presence of H2S. A detailed analysis was executed to determine the sensor's most suitable pH value and time. It was found that the optimum pH was 8.0, and the optimal duration was 15 s. It has been calculated that the linear range of the developed method is 2.19 × 10-8- 6.25 × 10-7 M, and the detection limit (LOD) is 7.37 × 10-9 M. The effect of some possible interfering ions was investigated, and it determined that the sensor had excellent selectivity. In addition, the sensor used to determine H2S can be used at least 100 times. The recovery percentages were 102.1%-103.2%, and 104.6%, using tap water samples. In terms of providing reliable, fast results, high sensitivity, reusable, low cost, and ease of use, the developed fluorimetric sensor, compared to standard methods, has become more advantageous.